Han Minxiao

Transient analysis and control for microgrid stability controller

This work develops a microgrid stability controller to support microgrid switching its operation mode and provide DG units in the microgrid with the additional functionality of working in island mode without changing their control strategies. When microgrid works in grid connected mode, microgrid stability controller compensate power variation and reduces power fluctuation. When the main grid is not available, microgrid operates in island mode, microgrid stability controller provide output voltage and frequency reference for DG units. Its operation is analyzed by studying its control strategies, islanding detection techniques and black box arc model of circuit breaker at the Point of Common Coupling (PCC). Furthermore this paper analyzes its transient characteristics based on the dynamic performance of the microgrid during a fault in distribution network. Simulation and experimental results validates the feasibility of the microgrid stability controller.

Power control analysis for variable speed pumped storage with full-size converter

Variable speed pumped storage (VSPS) with full-size converter can be an effective measure for automatic frequency control and balancing renewable generation power fluctuation. This paper mainly studies the modeling and control strategies of both the machine-side and grid-side converter, basing on the structure of VSPS with three-level full-size converter. The characteristics of power regulation are analyzed for both generator mode and motor mode. On a basis of the given reference power generated by the need of grid operation, the control strategy of active power and reactive power is described. Finally, the authors illustrate the effect of the VSPS with full-size system for the network power control with renewable generation with MATLAB/SIMULINK.

Direct virtual power control of VSC-HVDC for starting up of offshore wind farm

This paper proposes a direct virtual power control algorithm based on the direct power control with space vector modulation (DPC-SVM) for offshore wind farm connected VSC converter. This control algorithm extends the scope of the traditional DPC. By introducing the virtual power, the DPC can work before the wind farm starts up when the AC side of VSC is open and the voltage stability is achieved as well. The calculation of the algorithm is simple by using most of the original DPC-SVM modules. It maintains the controller structure unchanged before and after the wind farm starts up. The correctness and effectiveness of the proposed control algorithm is verified through simulation in PSCAD/EMTDC software.

A novel transfer switching strategy of solid static for duplex feeding

Voltage sag has become the main culprit to high quality power supply. Solid Static Transfer Switch (SSTS) for duplex feeding is a kind of power device which can effectively alleviate the voltage sags. SSTS will switch sensitive loads to the alternate source with better power quality when the preferred source is suffering voltage sags or interruption. In this paper, the operational principle of SSTS is introduced at first. The dq transfer + low frequency pass filter will be employed for voltage sag detection. The detection technique finds a balance between the fast response and robustness. Authors will give a novel switching technique to speed up the switching performance based on forced commutating and thyristor voltage detection. Finally, the validity and efficiency of the strategy is verified by using the electromagnetic transients simulation. The switching period can be limited within 5 ms which will not cause malfunction of sensitive loads.